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The Great Debate of Back Buttering Tile: Should You or Should You Not?
Oftentimes we get asked about back buttering tile. Is it important? In which cases should you? We've heard many opinions along the way and seen many debates, but here's the official stance from an authority we all trust.
Generally, it's recommended for natural stone tile; however, it is not always needed to get the appropriate amount of coverage on ceramic or porcelain tile. Let's look at this a little deeper with the help of the CTEF.
"To begin this discussion, we first need to define several words. According to the NTCA Reference Manual:
Back butter is defined as the spreading of a bond coat to the backs of ceramic tile just before the tile is placed.
Bond is defined as the adherence of one material to another.
Coverage is defined as a measure of the amount of material required to cover a given surface.
According to the CTEF Certified Tile Installer Manual, Transfer is defined as the required adhesion of a bonding material to the tile.”
3 Purposes of Back Buttering Tile
At this point, most of us would agree that back buttering is essentially applying a thin layer of mortar on the back of a tile with the flat side of your trowel. But why exactly is that useful? There are three simple purposes according to the CTEF:
1. Increases bond strength of the mortar
Primarily, it promotes the increased bond strength of the mortar to the back of the tile by keying or burning the mortar into the tile surface.
2. Fills voids on the back of the tile
Secondly, it fills the voids created by the embossed pattern on the back of the tile which creates a flat plane.
3. Can fill inherent tile warpage
Lastly, it can fill the inherent warpage of the tile (as long as the maximum mortar thickness designated by the manufacturer has not been exceeded).
One other thing to note is that back buttering is not what gives you adequate coverage and support. As the CTEF states, "coverage and support are achieved by using an appropriate trowel notch size and shape, directional troweling technique, and mortar selection and mixing."